How to read the orange ADR plate on a truck
The orange ADR plate on a truck splits into two numbers: the top Kemler code shows the hazard type, the bottom UN number identifies the substance.
Logifie Team
Logistics Technology Experts
The orange plate on a truck carrying dangerous goods is split into two halves: the top number is the Kemler code, a hazard identification number showing the type and intensity of danger, and the bottom number is the four-digit UN number identifying the exact substance being carried.
What does the top number on an ADR orange plate mean?
The top number is the Kemler code, the hazard identification number set out in ADR 5.3.2.3 . It has two or three digits: the first names the primary hazard (2 gas emission, 3 flammable liquid or gas, 4 flammable solid, 5 oxidising effect, 6 toxicity, 7 radioactivity, 8 corrosivity, 9 violent reaction), and further digits add secondary hazards. A repeated digit intensifies that hazard, so 33 signals a highly flammable liquid rather than an ordinary one, and a single-hazard substance takes a trailing zero, as in 30. A TMS built for regulated freight can automate this check against the shipment paperwork.
What does the bottom number on an ADR orange plate mean?
The bottom number is the UN number, a four-digit code from the UN Model Regulations identifying the exact substance carried, such as 1203 for petrol or 1830 for sulphuric acid. It does not describe the hazard type; it points to one entry in the dangerous goods list, which the transport document and the ADR class guide link back to packing group, labels and quantity limits. Mismatching the two numbers is a common ADR failure, which is why carriers moving regulated freight often route the paperwork through a Dangerous Goods Safety Adviser before the load leaves the yard.
When does a truck legally need to display an ADR orange plate?
A truck must display the orange plate whenever it carries dangerous goods above ADR's small-load exemption thresholds, correctly numbered on the front, rear and both sides. Directive 2008/68/EC extends these ADR rules to domestic transport across the EU, and the European Commission's dangerous goods policy confirms member states enforce them at roadside checks. Those checks tightened in 2026: Commission Delegated Directive (EU) 2025/1801 introduced a single harmonised inspection checklist and a three-tier risk classification, mandatory across all member states from 24 June 2026, so plate errors are now checked against one common EU-wide standard.
| Kemler digit | Hazard meaning |
|---|---|
| 0 | No secondary hazard |
| 2 | Gas emission from pressure or chemical reaction |
| 3 | Flammable liquid or gas, or self-heating liquid |
| 4 | Flammable solid, or self-heating solid |
| 5 | Oxidising (fire-intensifying) effect |
| 6 | Toxicity or risk of infection |
| 7 | Radioactivity |
| 8 | Corrosivity |
| 9 | Risk of spontaneous violent reaction |
| X (prefix) | Reacts dangerously with water |
Frequently asked questions
What does a doubled digit like 33 mean on a Kemler code?
A doubled digit means the hazard named by that figure is intensified rather than repeated as a separate hazard. 33 identifies a highly flammable liquid, a stronger hazard than a single 3, and the same logic applies to other repeated digits such as 44 or 99.
What does the letter X in front of a hazard number mean?
An X placed directly before the Kemler code means the substance reacts dangerously with water and must never be treated with water in an emergency. This prefix appears on the plate itself, for example X423, and is defined in ADR 5.3.2.3 alongside the digit meanings.
Do all trucks carrying dangerous goods need an orange plate?
Most do, but ADR sets small-load exemption thresholds below which plain transport documents suffice and the plate is not mandatory. Above those thresholds, every unit carrying the load, including trailers, must display correctly numbered plates on all four sides.
Where can you look up what a specific UN number means?
The UN number can be checked against the dangerous goods list in ADR itself or any current ADR reference table, which gives the proper shipping name, hazard class, packing group and special provisions tied to that number. Dispatchers handling regulated freight regularly keep this list built into their transport management system rather than looking it up manually.
Carriers ready to move correctly placarded ADR freight can join the Logifie carrier network .
